Method for identifying a component with physical characterization

ABSTRACT

The present invention provides a method for identifying components based upon selected physical characteristics. Initially, a characterization function that will produce a unique characterization value within a set of components, is (or has been) assigned to the set of components. The characterization function is a function of at least one physical characteristic that is shared by the components within the set of components. Next, the measurable physical characteristics defined as part of the characterization function are measured by testing. A characterization value, which is calculated from the assigned characterization function, is determined for each component. Each component that is to be subsequently identified is then identified by its associated characterization value.

The application Ser. No. 08/959,231 is related to and herebyincorporates by reference the application titled A SYSTEM FORIDENTIFYING A COMPONENT WITH PHYSICAL CHARACTERIZATION, filed on Oct.28, 1997.

1. TECHNICAL FIELD

The present invention relates generally to electronic componentidentification. In particular, the present invention relates to theidentification of electronic components based on their physicalcharacteristics.

2. BACKGROUND OF THE INVENTION

Many electronic devices are based on modules made by combining a numberof components on a printed circuit board or other substrate. Examplesare personal computer motherboards, fax modem add-on boards, memorymodules (e.g., DRAM, SDRAM), and device controller boards. For variousreasons, it is important to be able to automatically and efficientlyidentify, throughout the manufacturing process, the individualcomponents that are combined to form an electronic module. The assignedidentifier can then serve as the key or label for (or in) one or morefiles (usually electronic) that relate to the individual component. Forexample, after components have been installed into a module, it may bedesirable to program individual component test information into themodule as part of the manufacturing process or to track components forquality control purposes. Therefore, the particular components utilizedfor the module must be identified in order for their specific testinformation to be stored and then located for programming into themodule or for certain quality control studies to be done.

Some manufacturers apply a barcode label containing an identificationnumber during the initial testing stage of each component to identifyit. Each component's test information is then saved against its barcodeidentification number in a database. During module assembly, componentbarcode labels are scanned and the stored test information linked tothese scanned barcode identifiers is then retrieved and applied to themodule. This component identification and information retrieval methodis effective; however, the required added step of applying barcodes tothe components makes the process less efficient within the productionenvironment. This form of identification can also fail if the barcodelabel is lost, obscured or sufficiently damaged.

In another identification scheme, the necessary test information may belinked to an identifier number that is incorporated into the component'sfuse identification number. This identifier number can later be readduring module assembly. The component test information linked to thisidentifier can then be downloaded into a module programmer or for otheruses. Unfortunately, however, a limited number of componentmanufacturers utilize fuse identification. Therefore, thisidentification/information retrieval scheme is only effective for aqualified homogeneous set of components; thus, an acceptable "batch" ofinterchangeable components could not include components supplied from avariety of manufacturers.

When the electronic component is a memory component, some manufacturersuse a portion of the component's bit defect map as a unique`fingerprint` for identification of the particular component. In orderto identify the component, a bit error check on the appropriateaddresses is performed. The resulting bit error map can then be utilizedas an identifier to store and retrieve the entire test information filefor the component from a database. No label is added to the component. Adrawback of this identification method, however, is that, particularlywith low error rate components, a relatively large number of bitlocations must be used for the partial bit map identifier in order toproduce a unique `fingerprint` for each component. Thus, with thisscheme, excessive time is required for initial or subsequentidentification of a given component. Further, being based on errors, itdoes not work for devices with no defects or for devices with a low bitcount where there may exist no real or distinct pattern of bit-levelerrors.

Accordingly, what is needed in the art is an efficient electroniccomponent identification scheme that does not require the addition orexistence of external identification material and works for a widevariety of components.

3. SUMMARY OF THE INVENTION

The present invention provides a method for identifying individualcomponents based upon selected physical characteristics. In oneembodiment,, a characterization function that will produce a uniquecharacterization value for each individual component within a set ofcomponents is (or has been) assigned to the set of components. Thecharacterization function is a function of at least one physicalcharacteristic that is shared by all components within the set ofcomponents. Next, for each component, the measurable physicalcharacteristics defined as part of the characterization function aremeasured, and an individual characterization value, which is calculatedfrom the assigned characterization function, is determined. Eachcomponent that is to be subsequently identified is then identified byits associated characterization value. This characterization value canbe stored in a database as an identifier for information associated withthe component.

4. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts acts for implementing one embodiment of the presentinvention.

FIG. 2 depicts an embodiment of a system for determining a component'scharacterization value.

FIG. 3 depicts acts for implementing another embodiment of the presentinvention.

FIG. 4A shows an embodiment of a system for producing a memory moduleutilizing physical characterization to identify components and retrievecomponent-specific data.

FIG. 4B shows a second embodiment of a system for producing a memorymodule utilizing physical characterization to identify components andretrieve component-specific data.

FIG. 5 depicts a block diagram of an embodiment of a memory module.

5. DETAILED DESCRIPTION

The present invention relates to the identification of electroniccomponents based upon selected inherent physical characteristics.Electronic component identification by physical characterization, aswill be discussed in greater detail below, may be utilized in a varietyof settings. In particular, physical characterization identification ofcomponents may be exploited in various production applications includingcomponent information retrieval, module programming, and componentmanufacturing quality control. Identification by physicalcharacterization is beneficial because added identification "tags" or"marks" (e.g., barcodes, fuse identification numbers) are not required.In addition, a sufficient number of physical characteristics, which arenecessary to produce a unique identification value for each component,may be measured in a relatively minuscule amount of time, thereby makingthis process valuable in a production environment.

As used herein, the term "component" includes any electronic componentpossessing a sufficiently diverse array of measurable physicalcharacteristics that make it amenable for physical characterization astaught by the present invention. Such components may be analog, as wellas digital, semiconductor devices and include, but are not limited to,memory devices, interface components, latches, amplifiers, and otherintegrated microcircuit components.

5.1 Component Identification with Physical Characterization

FIG. 1 generally depicts acts for identifying components by usingphysical characterization. Initially, at 110, a characterizationfunction that will produce a unique characterization value for eachcomponent within a set of components, is assigned to the set ofcomponents. Next, at 120, the individual characterization value isdetermined by measurement for at least one component within the set ofcomponents. Finally, at 130, the component to be identified isassociated with its unique characterization value, which serves as itsidentifier. Typically, this association requires recording theindividual characterization value in a record-keeping system, such as acomputer database.

5.1.1 Physical Characterization Function Assignment

As a first step in employing the present invention, a physicalcharacterization function is assigned to a set of components. Thefunction may either be selected from an existing physicalcharacterization scheme, or it may be derived (or created) for the setof components. The primary considerations in assigning (i.e., selectingor creating) a characterization function are: (1) it should produce aunique characterization value for each component within the set ofcomponents, and (2) the physical characteristics, which are theindependent variables of the characterization function, should bereadily measurable to an acceptable degree of resolution within thecomponent identification environment.

There are two aspects to the assignment of the characterization functionto a set of components: the set of components and the characterizationfunction itself.

5.1.1.1 Component Set

A component set may be any set of components sharing a sufficient numberof physical characteristics that enable a single characterizationfunction to be assigned to the set. The set may or may not behomogeneous with respect to the type and producer of the components thatconstitute the set. For example, a given set of components could includemultiple types of memory devices such as RAMs (random access memory) andPROMs (programmable read only memory). In contrast, a set could alsoconsist of components of a particular type, e.g., DRAM (dynamic RAM)that may or may not have originated from the same manufacturer or thesame production lot. However, the shared physical characteristics thatare used for the assigned characterization function should be measurablefor each component within the component set without knowledge of theparticular component being measured. Thus, the necessary electricalcontacts (e.g., pins), as well as any required initialization andset-up, must be sufficiently compatible for consistently measuring thecomponents' relevant physical characteristics, both for an initialdetermination and subsequent identification.

5.1.1.2 Characterization Function

A characterization function is a mathematical function that both (1)depends upon at least one measurable physical characteristic sharedwithin a set of components, and (2) produces a unique characterizationvalue for each component for a given set of measurement conditions.Thus, a characterization function should depend upon physicalcharacteristics (a) whose normal range sufficiently varies from onecomponent to another within a component set, and (b) which varies withinan easy sensitivity range for the test equipment used to measure thecharacteristics. For a particular component, the characterizationfunction should provide a consistent characterization value (or at leasta value predictably varying within an acceptable range), each time itscharacterization value is determined. This may (and more than likelywill) mean that relevant physical characteristics (i.e., those measuredcharacteristics on which the characterization function depends) willeither be measured within a tolerable range of test/measurementconditions (e.g., temperature, supply voltage, output impedance), or thefunction will be defined to depend upon various test/measurementcondition variables in addition to relevant physical characteristics.

The term "physical characteristic" refers to the measurable physicalcharacteristics that are associated with semiconductor components. Thedifferent measurable physical characteristics that make up acharacterization function can consist of (1) a combination of differentphysical parameters (such as DC electrical characteristics, e.g., outputleakage current, output high voltages, and output low voltages;operating currents; capacitances; and AC electrical characteristicsincluding delays and access times), and/or (2) a single physicalparameter (such as the actual output high voltage value V_(OH))occurring at a combination of different physical locations within thecomponent. Preferably, the characteristics chosen are ones that can bemeasured consistently both before the component is installed and atvarious stages of production of the module in which it is incorporated.Although a characterization function could be defined as a vector orarray consisting of each of the individually measured values, storingsuch a value could consume many bits of storage. Thus, the individuallymeasured values will normally be combined in some fashion by thecharacterization function to produce a compressed but still uniquevalue.

As used herein, "combining" means using any algorithm by which theindividual measured values used in a characterization function arebrought together by compression (without loss of information) or byaddition, multiplication, weighted summing or other mathematical orlogical operations in which information may be lost, while stillproducing a unique identifier for each component in numeric,alphanumeric or other computer-storable form.

As an example, consider a component set that consists of a number of RAMdevices (e.g., a number of 4M ×4 row/column accessible RAM chips). Thecharacterization function assigned to this set must depend upon asufficient number of varying physical characteristics (from component tocomponent) to ensure that a unique characterization value will bedetermined for each component. On the other hand, however, the number ofnecessary physical characteristics is preferably kept low, so that theamount of time required to make the measurements to determine acharacterization value for a given component also will be reduced. Withcomponents such as memory devices, which include vast pluralities ofmemory cells (16 million for each device in this example), a goodstarting place for relevant physical characteristics is to look at thephysical characteristics of a subset of the individual cells.

Thus, in this example, a suitable characterization function could simplydepend upon the individual output high voltages (V_(OH)) for a givendefinable set of cells. For example, the following characterizationfunction could be assigned to the component set for a given temperature,supply voltage, and output impedance:

    CV=sum of the highest 200 V.sub.OH levels within the first 40 rows

where CV is the characterization value and V_(OH) is the output highvoltage level for a given cell. In this example, because each rowconsists of four cells, the characterization value will equal the sum ofthe 200 largest cell output high values for the first 800 cells. Withthis function, the highest values within an arbitrary cell range areutilized in order to reduce the averaging effect of combining (bysumming) a large number of individual cell values, which could preventthe function from producing a unique characterization value for eachcomponent within the set. However, the efficacy of the function in thisregard also depends upon the resolution and precision of the teststation used to measure the individual cell values.

Another possible solution to the averaging problem, is to weight variouscell values differently as they are combined. For example, anotherpossible characterization function for a given temperature, supplyvoltage, and output impedance is as follows: ##EQU1## where r representsrow, c represents column and b represents bit. Thus, individual bit cellvalues are weighted differently based upon their bit location, therebyreducing the averaging nature of the summing. Again, however, theeffectiveness of this function in a physical characterizationidentification scheme ultimately depends also upon the precision andresolution of the test station used to measure the relevant physicalcharacteristics.

Another possible approach in formulating a characterization functionthat produces a unique value for each component within the set ofcomponents is to utilize a relatively wide variety of physicalcharacteristic types as relevant physical characteristics and weightthem differently. For example, the following characterization functioncould be utilized with consistent operational conditions (e.g.,temperature, supply voltage, output impedance) for a set of memorydevices. ##EQU2## where I_(cc) is operational supply current, t_(ZL) isthe time delay (referenced from a "switching" signal such as a clock ora read signal, depending upon the particular component type) for a givencell to change from a state of high impedance to low, V_(OL) is theactual value of a cell's low output, and V_(OH) is the actual value of acell's high output.

It should be recognized that a wide variety of possible effectivecharacterization functions can be either created or selected for mostcomponent sets. Again, however, the function should produce aconsistent, unique characterization value for each component within agiven component set, which may then be used as an identifier. Theappropriate physical characterization function may vary from company tocompany for the same type of component. One manufacturer may have asuitable range of normal variance for access time, while another mayhave too tight a range on this variable but a more suitable normalvariance range on output voltages on another characteristic. Once aphysical characterization function is selected, its effectiveness forproducing an adequately dispersed (and therefore distinct) set ofcharacterization values can be tested for a given population ofcomponents.

5.1.2 Characterization Value Determination

To initially determine the characterization value of a component, itsrelevant physical characteristics are measured under a prescribed set ofmeasurement conditions (as may be dictated by its characterizationfunction). The characterization value is then determined with thesephysical characteristic measurements "plugged" into the characterizationfunction. With a properly chosen characterization function, theresulting characterization value will be unique for each component andcan thus be used as an identifier.

The characterization value may be any number (e.g., real number orinteger) that is suitable as an identifier for the measured component.In addition, the characterization value could also be an array ofnumbers, each corresponding to a different relevant physicalcharacteristic or combination thereof, depending upon the nature of thecharacterization function assigned to the component set. With thislatter type of characterization value, a multiple value array (orvector) would serve to uniquely identify each component within acomponent set.

FIG. 2 depicts a system for determining a component's characterizationvalue. A characterization value test station 50 is electronicallycoupled to component 16, which, by way of example, is a 4M ×4 row/columnaccessible RAM memory device. The characterization value test station 50is also coupled to a personal computer 35, which is capable ofmonitoring and controlling test station 50.

The characterization value test station 50 is utilized to measure acomponent's relevant physical characteristics. It may be implementedwith any test station or test equipment capable of measuring acomponent's relevant physical characteristics within acceptableresolution and tolerance ranges, under any set of measurement conditionsthat may be prescribed by the characterization function. For example,with a memory device component set, the characterization value teststation 50 could be implemented with a memory tester such as a TeradyneJ994™ available from Teradyne, Inc. of Boston, Mass., an Adventest 8551™available from Adventest of Tokyo, Japan, a Genesis G2™ available fromTeradyne, Inc. of Boston, Mass., or a Sigma II™ available from Darkhorseof Austin, Tex. It can be seen that the particular characterizationfunction that may be assigned to a given set of components will dependupon the capabilities of the characterization value test station that isavailable or that can be designed for the component set.

Computer 35, which is also connected to a network server 30, is utilizedto monitor and control the characterization value test station 50. (Itshould be recognized, however, that depending upon the particularequipment utilized to implement test station 50, computer 35 may or maynot be necessary for its monitoring and control). In addition, thecomputer 35 may be used to calculate (and, thereby, determine) thecharacterization value from the physical characteristic measurementsobtained by the characterization value test station 50. Persons ofordinary skill in the art will recognize that this characterizationvalue determination may be implemented by computer 35 with softwaredesigned to calculate the particular characterization function. Thecharacterization value could also be determined by software within thenetwork server 30 or the characterization value test station 50.

5.1.3 Component Identification

Component identification by physical characterization is the associationof a component with its characterization value, for use as thecomponent's "identifier." While this association can be confirmed with alabel affixed to or in the component, physical characterization makesthis unnecessary. Proper selection of the characterization functionresults in each component inherently carrying its own identifier, basedon the particular variants of the relevant measured physicalcharacteristics present in the component. Thus, with this scheme,whenever a component is to be identified (or "labeled"), itscharacterization value is determined (by measurement and calculation)and recorded in some form, preferably by storage in a computer databaselist of components.

For an unknown (but previously identified) component, the identificationis recovered by repeating measurements and calculations to determine thecharacterization value. Once this value is determined, the component hasits identifier. To recover information associated with the identifier,the identifier is matched (or referenced) against characterizationvalues that were originally determined and stored (e.g., in a database)for at least one component within a set of components. Assuming acharacterization value was originally determined for any component thatis in the database, a match will occur or may be "forced" based upon apre-defined criterion or criteria. For example, a characterization valuecould be forced to match the closest of the referencedoriginally-determined characterization values. This "forcing" isutilized to compensate for non-ideal conditions, which may result in atleast somewhat inconsistent characterization value determinations for agiven component.

Component identification of this sort can be utilized in severalcontexts. In one embodiment, the originally determined characterizationvalue identifiers can be organized into various groups. For example, thegroups can be organized by production lot, manufacturer, tolerance, ordefect level. Thus, a component is then attributed with the commonqualities of a group of components to which it belongs. These qualitiescan be linked in the database to a stored list of identifiers for eachcomponent in the group. This may facilitate inventory or quality controlfor components in the group.

In another embodiment, each originally determined characterization valueidentifier is linked in the database to unique information pertaining tothe component. With this embodiment, once a characterization valueidentifier has been found in the database, the information that islinked to the identifier can be retrieved and utilized in connectionwith the identified component. Information retrieval based on a physicalcharacterization identifier is discussed in greater detail below.

5.2 Component Information Retrieval By Physical Characterization 5.2.1In General

FIG. 3 shows the general acts for retrieving information after physicalcharacterization identification. Initially, at 210, a characterizationfunction is assigned to the given set of components. At 220, thecharacterization value is initially determined and linked to componentinformation for at least one component (and more than likely for eachcomponent) within the set of components. Thereafter, the components maybe mixed with each other, so that any visible individual identificationis lost. Later, at 230, the characterization value is again determinedfor a component for which information is to be retrieved and whosecharacterization value was initially determined in the previous act. At240, information that is linked to the later determined characterizationvalue is then retrieved. This retrieved information will pertainspecifically to the component for which information is to be retrieved.

The system of FIG. 2 may be utilized to implement this physicalcharacterization information retrieval process. A database program 32may be executed by network server 30 (or alternatively by computer 35 orcharacterization value test station 50 ). With such a database program,information pertaining to each component within a component set may bestored in a record. The record for a particular component may then belinked to that particular component's characterization value, after ithas been determined. Thus, component characterization values are used asidentifiers for the component records of the database.

In one embodiment, known information pertaining to a given component isstored in a selected record of the database. The component'scharacterization value is then determined at test station 50 andsubsequently stored in the same selected record to be used as anidentifier for the component. After the characterization value has beendetermined for each component and stored as an identifier in a distinctrecord, along with information pertaining to the component, thecomponents may be combined or "mixed-up" together. Thereafter, ifinformation pertaining to a selected component is needed, itscharacterization value is determined by testing and the database recordthat contains this value is retrieved along with the other informationthat pertains to the component.

Information pertaining to a component may be any type of informationincluding: manufacturer, tolerance, and test information, such as defectmapping. In one exemplary embodiment of the present invention, thecomponents are memory devices and a memory tester (e.g., a TeradyneJ994™ available from Teradyne, Inc. of Boston, Mass.) is used as thecharacterization value test station 50. For each memory device 16 from aset of memory devices, the memory tester determines a device'scharacterization value (which usually takes only a few seconds) andtests the device for bit defects (which may take several minutes, as allbits are tested). The bit defect information and characterization valueare stored together in a database record to link the characterizationvalue as an identifier to the bit defect information. After all of thedevices have been tested and linked to their characterization value,they can then be combined and distributed for manufacturing or otherprocesses without requiring any added marks or identification materials.Whenever the bit defect information is required for a given component,the component's characterization value is determined and used toretrieve the component's bit defect information from the database.

The retrieved component information can be used in a variety of ways.One particular use is in manufacturing a module in which themanufacturing must be accommodated to individual componentcharacteristics. As will be explained in the next section, with furtherreference to the example of a memory device 16 for which bit defectinformation has been stored, the defect information can be used tomanufacture a module in which the component-specific defects arecircumvented.

5.2.2 Memory Module Production 5.2.2.1 Memory Module

The term memory module refers to any electronic module that includes oneor more memory devices. A memory device is a component that includesmemory cells for storing bit information. Memory devices may be, but arenot limited to, RAM (random access memory), DRAM (dynamic random accessmemory), EDO DRAM (extended data DRAM), SRAM (static random accessmemory), VRAM (video random access memory), PROM (programmable read onlymemory), or EPROM (erasable PROM).

Memory devices can contain millions of memory cells, only a few of whichmay be defective. Thus, it is desirable to utilize "defective" memorydevices (i.e., devices that contain at least one defective cell) inmemory modules that overcome the defects rather than completelydiscarding such devices.

FIG. 5 depicts one embodiment of a scheme for effectively using memorydevices (which may or may not be defective) in a memory module. Memorymodule 10 includes: memory 15, memory recovery interface 12, and EPROM13. Memory 15 further includes memory devices 16a-d and decoder 17. (Theactual memory module corresponding to the memory module 10 would alsoinclude a base, e.g., a printed circuit board, not shown, for housingthe various constituent components). The memory recovery interface 12 iscoupled to host processor 14, memory 15, and EPROM 13.

Memory recovery interface 12 serves as an interface between a hostprocessor 14 and memory 15. It can be any device (or device combination)that provides to host processor 14 access to memory 15 withoutalteration of the processor's addressing scheme, while preventing anydefective memory cells of memory 15 from being used by the hostprocessor 14. In one embodiment, memory recovery interface 12 is amemory controller (or combination of read and write memory controllers),as taught by pending U.S. application Ser. No. 08/802,895 now U.S. PatNo. 5,958,065 as of Sep. 28, 1999 entitled CONTENT ADDRESSABLE BITREPLACEMENT MEMORY, filed on Feb. 18, 1997, which is hereby incorporatedby reference into this specification. The memory controller orcontrollers may be implemented with an ASIC (application specificintegrated circuit). With this memory controller embodiment, the memoryrecovery interface 12 effectively replaces bad cells (or bytes) frommemory 15 with good cells (or bytes) from elsewhere (e.g., within memoryrecovery interface 12 ).

In a second embodiment, memory recovery interface 12 is a logical tological translator, which diverts access from a bad to a good bytethrough logical to logical translation. This can be accomplished whenmemory 15 includes more memory than is required by host processor 14.

Memory devices 16a-d and decoder 17 are organized into a conventionalmemory array to form memory 15. The four 4M×4 RAM devices are convertedinto a 16M×4 RAM having 14, rather than 12, address lines. (It ispresumed that with each row/column accessible RAM 16a-d, row and columnaddresses are input separately to the device through a common 12-bitaddress bus. 12 lines are used for a row address and 10 lines for acolumn address.) Thus, each 4-bit byte is directly accessible to thememory recovery interface 12. In turn, with bit error information (i.e.,defect locations) of memory 15 available to memory recovery interface12, memory recovery interface 12 can provide to host processor 14 accessto memory 15 without alteration of the processor's addressing scheme,while preventing any defective memory cells/bytes of memory 15 frombeing used. The bit error information is provided to memory recoveryinterface 12 through EPROM 13 (e.g., the information could be downloadedinto internal memory of memory recovery interface 12 during start-up).

5.2.2.2 Embodiment of a Memory Module Production System

FIGS. 4A and 4B show embodiments of a system for producing a memorymodule. Each embodiment includes: a memory test station 20, a computer35, a network server 30, a module assembler 40, a characterization valuetest station 50, and a module programmer 60.

Initially, memory devices from a set of memory devices are batch testedfor bit defect information at memory test station 20. (Memory teststation 20 may be any device or combination thereof that can test andmap memory devices for bit errors, as well as determine characterizationvalues for each device. Such a memory test station could be implementedwith a memory tester including a Teradyne J994™ available from Teradyne,Inc. of Boston, Mass., an Adventest 8551™ available from Adventest ofTokyo, Japan, a Genesis G2™ available from Teradyne, Inc. of Boston,Mass., or a Sigma II™ available from Darkhorse of Austin, Tex. Memorytest station 20 also determines the characterization value for eachmemory device and stores this value, along with the device's bit defectinformation, in a record of a database, which may be resident withintest station 20, computer 35 or network server 30. With the embodimentof FIG. 4A, a characterization value test station 50 (which may beseparate or may be implemented as part of memory test station 20)determines the characterization values for the devices that are to beinstalled into a memory module. With these values, it retrieves thedevice's bit defect information and provides this information to moduleassembler 40. The module assembler 40 then installs the devices into themodule base. Finally, the module programmer 60 programs the bit defectinformation into the memory module (e.g., it "burns" the informationinto EPROM 13 of FIG. 5).

With the embodiment of FIG. 4B, the characterization value test station50 is functionally after, rather than before, of module assembler 40.With this embodiment, memory devices from the set of devices areprovided to the module assembler 40 after being tested. Here, they areinstalled into a memory module base. The module is then provided tocharacterization value test station 50, which includes a loadboard forelectrical access to the individual memory devices within the module.The device characterization values are each determined, and their bitdefect information is retrieved and provided to module programmer 60.(It should be recognized that with this latter embodiment, acharacterization function should be assigned that can toleratedeviations in a device's measured physical characteristics, which mayoccur when the devices are initially measured individually and, later,as part of a module.)

5.2.3 Component Grade Screening

Retrieved information that is specific to a component may also be usedin production processes where products of more than one grade areproduced. For example, a product may be made in a commercial grade and amilitary grade whose components with tighter tolerances or betterperformance characteristics are required. In the production process theindividual components can be identified by their characterization valueand a file containing tolerance or quality information retrieved. Theretrieved information can be measured against a screening criterion (orcriteria). Depending on whether the component meets the criteria or not,the component can be used in production with the higher grade productsor the resulting product can be marked as either the higher or lowergrade.

5.3 Remarks

A primary benefit of the present invention is that it permits componentsthat are to be assembled in a production process to be identifiedwithout needing to apply any physical identifying label to thecomponent. An additional benefit is that the identifying physicalcharacteristics selected as the basis for the initial (and subsequent)identifier for each one of a set of components can be determined in arelatively short period of testing, consistent with on-the-flyidentification in production processes. A further benefit is that eachidentifier can be easily stored in a computer database in associationwith, and used as a retrieval key for, other information particular tothe component identified by the identifier.

5.4 Other Embodiments

While the present invention has been described with reference to severalembodiments thereof, those skilled in the art will recognize variouschanges that may be made without departing from the spirit and scope ofthe claimed invention.

Accordingly, the invention is not limited to what is shown in thedrawings and described in the specification, but only as indicated inthe appended claims.

What is claimed is:
 1. A method for identifying a component, the methodcomprising:assigning for a set of components a characterization functionthat produces a unique characterization value for each component withinthe set of components, wherein the characterization function is afunction of at least one measureable physical characteristic shared byeach component within the set of components; determining thecharacterization value of at least one component within the set ofcomponents; associating the at least one component with itscharacterization value as an identifier such that the at least onecomponent, is re-identifiable by the characterization function; andlinking information associated with the at least one component to itscharacterization value.
 2. The method of claim 1, wherein the act ofdetermining the characterization value for at least one componentincludes the acts of:measuring a plurality of physical characteristicsfor the at least one component, thereby producing a plurality ofphysical characteristic measurements, and combining the plurality ofphysical characteristic measurements to determine the characterizationvalue.
 3. The method of claim 2, wherein the act of assigning for a setof components a characterization function includes assigning for a setof memory devices a characterization function.
 4. The method of claim 3,wherein the act of measuring a plurality of physical characteristics forthe at least one component includes measuring at least one physicalcharacteristic for each of a plurality of memory cells.
 5. The method ofclaim 2, wherein the act of combining the plurality of physicalcharacteristic measurements to determine the characterization value fora component includes the act of weighting at least one of the physicalcharacteristic measurements for the component.
 6. The method of claim 1,wherein the act of determining the characterization value for at leastone component comprises:measuring a plurality of DC characteristics forthe at least one component, thereby producing a plurality of DCcharacteristic measurements, and combining the plurality of DCcharacteristic measurements to determine the characterization value. 7.The method of claim 6, wherein the act of assigning for a set ofcomponents a characterization function includes assigning acharacterization function for a set of memory devices.
 8. The method ofclaim 7, wherein the act of measuring a plurality of DC characteristicsfor the at least one component includes measuring at least one DCcharacteristic for each of a plurality of memory cells.
 9. The method ofclaim 6, wherein the act of combining the plurality of DC characteristicmeasurements to determine the characterization value for a componentincludes weighting at least one of the DC characteristic measurementsfor each component.
 10. The method of claim 1, wherein the act ofassociating the at least one component with its characterization valueas its identifier includes the act of recording the characterizationvalue as an identifier in a list of identifiers, the list correspondingto a group of components that share common qualities.
 11. The method ofclaim 1, wherein the act of associating the at least one component withits characterization value as its identifier includes the act of storingin a database the characterization value as an identifier that is linkedto information pertaining to the at least one component.
 12. A methodfor retrieving information on a component, the methodcomprising:assigning for a set of components a characterization functionthat will produce a unique characterization value for each componentwithin the set of components, wherein the characterization function is afunction of at least one measurable physical characteristic that isshared by each component within the set of component; for each of aplurality of components within the set of components, determining itscharacterization value and linking that value to the component as anidentifier and to information pertaining to the components; determiningby subsequent testing the characterization value of a first componentfrom the plurality of components thereby re-identifying the firstcomponent; and retrieving information that is linked to the determinedcharacterization value of the first component, whereby the informationpertains to the first components.
 13. The method of claim 12 furthercomprising: (1) utilizing the first component as part of an electronicmodule, and (2) programming the retrieved information into theelectronic module.
 14. The method of claim 13, wherein the act ofassigning for the set of components a characterization function includesassigning for a set of memory devices a characterization function. 15.The method of claim 14, wherein the act of programming the retrievedinformation into the electronic module includes programming defectinformation into the electronic module.
 16. The method of claim 13,wherein the act of determining by subsequent testing thecharacterization value of a first component from the plurality ofcomponents includes measuring physical characteristics of the firstcomponent after it has been installed into the electronic module. 17.The method of claim 12 further comprising utilizing the first componentfor an electronic module if the retrieved information satisfies ascreening criterion.
 18. The method of claim 12, wherein an act ofdetermining the characterization value of a component comprises: (1)measuring a plurality of physical characteristics for the component,thereby producing a plurality of physical characteristic measurements,and (2) combining the plurality of physical characteristic measurementsto determine the characterization value of the component.
 19. The methodof claim 18, wherein the act of assigning for a set of components acharacterization function, includes assigning for a set of memorydevices a characterization function.
 20. The method of claim 19, whereinthe act of measuring a plurality of physical characteristics for thecomponent includes measuring a physical characteristic of a memory cellfrom the component.
 21. The method of claim 20, wherein the act ofcombining the plurality of physical characteristic measurements todetermine the characterization value of the component includes weightinga group of physical characteristic measurements.
 22. The method of claim12, wherein an act of determining the characterization value of acomponent comprises (1) measuring a plurality of DC characteristics forthe component, thereby producing a plurality of DC characteristicmeasurements, and (2) combining the plurality of DC characteristicmeasurements to determine the characterization value.
 23. The method ofclaim 22, wherein the act of assigning for a set of components acharacterization function includes assigning for a set of memory devicesa characterization function.
 24. The method of claim 23, wherein the actof measuring a plurality of DC characteristics for the componentincludes measuring a DC characteristic for each of a plurality of memorycells from the component.
 25. The method of claim 24, wherein the act ofcombining the plurality of DC characteristic measurements to determinethe characterization value includes the act of weighting at least one DCcharacteristic measurement.
 26. A method for producing an electronicmodule having a memory that includes at least one memory device from aset of memory devices, the method comprising;testing each of a pluralityof memory devices from the set of memory devices, the testing for eachmemory device including:acquiring test information on the device,determining a characterization value for the device, wherein thecharacterization value is determined from a physical characterizationfunction that has been assigned for the set of memory devices and thathas been determined to produce a unique characterization value, linkingthe test information on the device to the unique characterization valuesuch the unique characterization value identifies the test information:storing in a database the test information linked to thecharacterization value, wherein the test information for each of theplurality of memory devices is retrievable from the database with thedevice's characterization value; installing a first memory device, fromthe plurality of memory devices, into an electronic module; determiningthe characterization value of the first memory device therebyidentifying the first memory device; with the determinedcharacterization value, retrieving from the database the testinformation for the first memory device; and programming the retrievedtest information into the electronic module.
 27. The method of claim 26,wherein the act of programming the retrieved test information into theelectronic module comprises programming bit defect information for thefirst memory device into a programmable memory device.
 28. The method ofclaim 27, wherein the act of programming bit defect information for thefirst memory device into a programmable memory device comprisesprogramming the bit defect information into a programmable memory devicethat is accessible to a memory recovery interface of the electronicmodule.
 29. A method for producing a memory module having (1) a base,(2) memory including a first memory device, and (3) a memory recoveryinterface to interface between a host processor and the memory, whereinthe memory recovery interface provides the host processor access to thefirst memory device without requiring alteration of the processor'saddressing scheme, while preventing any defective memory cells of thefirst memory device from being used by the host processor, the methodcomprising:testing each of a plurality of memory devices from a set ofmemory devices that each include a plurality of cells, the testing foreach memory device including:acquiring defect information for the cellsof the device, determining a characterization value for the device,wherein the characterization value is determined from a physicalcharacterization function that has been assigned for the set of memorydevices and wherein the characterization value for each device will be aunique product of the physical characterization function such thatcharacterization value identifies the device; and linking thecharacterization value to the defect information; storing in a databasethe defect information linked to the characterization value, wherein thedefect information for each of the plurality of memory devices isretrievable from the database with the device's characterization value;installing a first memory device, from the plurality of memory devices,into a base; determining the characterization value of the first memorydevice thereby identifying the first memory device; with the determinedcharacterization value, retrieving from the database the defectinformation for the first memory device; and programming the defectinformation for the first memory device into the module thereby enablingthe memory recovery interface to prevent defective cells from beingused.
 30. The method of claim 29, wherein the act of programming thedefect information into the electronic module comprises programming alogic device based on the defect information.
 31. The method of claim30, wherein the act of programming a logic device comprises storing thedefect information into a programmable memory device that is accessibleto the memory recovery interface.